1. Field of the Invention
The present invention relates to an insulating substrate obtained by impregnating a glass woven fabric with an epoxy resin or a circuit board (also referred to as a printed board) made of plastic, ceramics, or the like, on a surface of which a chip-shaped electronic component is provided, or a mount structure of a chip-shaped electronic component mounted on a circuit board by solder. In particular, the present invention relates to a mount structure of a chip component having at least two terminals.
2. Description of the Related Art
In recent years, high-density mounting of a chip component on a circuit board has been attempted for reduction in size of electronic appliances. Therefore, a mount structure which needs an area larger than the area of a chip component, such as a lead frame structure in which a side surface of a ceramic or plastic box shape has leads like legs, is not suitable to high-density mounting. A structure called CSP (chip size package) has attracted attention in which electrodes are provided on a bottom surface (undersurface) of a chip component so that an area necessary for mounting is substantially as large as an area occupied by the chip component even after mounting the chip component in order to achieve higher density without using such a lead frame structure. CSP makes it possible to electrically connect a terminal electrode of a chip component and a connecting electrode of a circuit board through the shortest current path and thus shorten a distance between chip components and achieve high-density mounting.
Further, a photoelectric conversion element of which electrode is provided on a bottom surface (undersurface) of a chip component is disclosed in Patent Document 1.
A connecting electrode provided on a circuit board has an area as large as or larger than the area of a terminal electrode of a chip component. Note that the connecting electrode provided on the circuit board is also referred to as a land. BGA (ball grid array), LGA (land grid array), and the like are given as other mounting technologies.
Further, a procedure to mount a chip component on a circuit board is described. First, cream solder is supplied by using a mask having an opening whose shape is substantially the same as that of a connecting electrode of the circuit board to print the cream solder on the connecting electrode of the circuit board. Then, the chip component is mounted on the circuit board so that the connecting electrode is overlapped with the terminal electrode with the cream solder therebetween with a surface of the chip component, on which the terminal electrode is provided, facing downward. After that, reflow solder mounting is performed.